Someone has to have run into this problem. I had a VERY MUSSHY Brakes on my 1998 F150 ext.cab 5.4 rear Anti Lock brakes so:
1) changed Frt pads, rotorsand hoses also rear drums, shoes and w/cylinders.
2) changed Mastercylinder (2 twice)
3) changed Power Booster
4) Fushed and drained entire brake system 18 trimes.
5) NO ABS light on dash or check engine light or no codes thrown.

NOW FOR THE PROBLEM!!: It seems that EVERY TIME I turn off the engine (go into a store) and start it back up I have little or NO Brake pedal. Give it two or three pumps and continue I have Great Brake Pedal. Shut it off-Same problem. It's cost me a bundle to STILL have this same Rat B------d problem. Either I get some help or I am buring this Piece of ***** in the front yard!!
Sorry. Do I sound Pi$$ed??
Someone HELP ME!! PLEASE help:
Out of money!!!
Thanks,
Dan:

 

when you replaced the booster did you replace the hose to the manifold? if so check it for leaks.

Check to make sure your calipers are floating free and easy.

follow your rear brake lines from the front of the truck down to the frame and look for a distribution box (I am not sure if these trucks have them) if you find one it will prolly have a bleeder screw on it. it is prolly full of air if you bled your brakes the old fasion way.

even though it is a new part the booster could be bad.

my .02 good luck

 

I have very mushy brakes and suffer from the same problem you have. THis is absurd how difficult it is to get our 97 and 98 trucks to stop. I am hoping i can find a larger brake booster from a 02 truck, i just cant find out if it fits or can be put on my truck. My fathers 02 supercrew has brakes like a lexus. His brake booster is more than twice the size of mine. I am still in search of the answers.

 

I have a 97...you have to make sure the rear linings are adjusted out ..lift both wheels put in nuetral and spin the wheels..adjust the brakes till you hear them just scrapping the drums...apply pressure to the brakes and check your adjustments again..if after a while they go soft again you may need to look at your self adjusters..mine did and when I look at the lever contacting the star wheel it had a knotch cut in it and was only skipping across the wheel...the dealership sells a replcement kit for those heres the # F75Z-2A176-AA ...it's funny how it contains both sides and not only the lever but the springs and the piece that the cable from the top wraps around on it's way down to the lever itself...hhhmmm think ford knows of a problem here ?...oh yeah $17.53 american

 

Hey all, got my BRAKES DONE on a 98 F150 54k . Everything has always been tight and responsive... now the brakes are squashy...hmmm... my trucks gone soft.. I've done the front 6 months ago...cake.... but something with the calaber... It hosed up.. Now... 700 $ on the whole system... is.... now ... squashy...

good luck all

 

I've always heard that driving in reverse while breaking should cause the rear to adjust?

Either way I know what you mean, I've had the pedal from hell on my 98 since January and it's been way too cold out here in Michigan to try and do anything about it so I've had to leave it parked in my driveway for the better part of the last few months. It is going to be warmer this week so I was going to replace all the linings and the rotors and drums. Then in an attempt to bannish the mushy pedal I was going to flush out the entire system. Only thing is, after reading this I'm wondering if it'll be worth my time. Please tell me you were able to get the pedal back to a solid feel. This is the one thing that I miss from when my truck was new, it could stop on a dime, now it seems to take forever.

 

Ok, It sounds like you have an air bubble in the system. These guys can be a real pain especially with all the fluid control valves we now have. This is not toally unsusal. The likely answer.....have to go to a mechanic who has a "reverse flow (preferred) presure bleeder. It may even take them between a couple of hours to all day to get that air out.

 

Sounds like a plan. Cool.